91 240sx overheating!!!

[whitebride91]

hello, im new and this is my first post. my car took a three hour drive back to my place and when we arrived in town, the temp was rising almost to the H. next day, i decided to drive it around and punch it around 4500 rpm and it took the beating without the temp rising(temp was near the center of C and H but a little lower). then i drove it to my brothers house and the temp stayed the same. couple days later, we checked for the thermostat and there wasnt any. the radiator was new so we changed the water pump and threw in an oem thermostat. the temp for the car still rose to the H after we bled the radiator and drove it around the block(regular driving not punching it). we also flushed the radiator and the top part of the engine where the radiator fluid runs through. now im not sure what to do. should i run without a thermostat like before? help please!!!

[elchoccolatte]

Keep the thremostat in, If the water pump has been replaced along with hoses, I would recommend doing a pressure test on the cooling system

[whitebride91]

how would i do a pressure test on this? are there side effects to running without a thermostat?

[positron1]

Friend of mine had it turn out to be something so simple...bad seal on his radiator cap. Replaced it and problem fixed.

[whitebride91]

my cap was a 16 psi cap. now im running a 12 psi cap to see what happens. hopefully its just the cap then. anymore problems ill ring them up. thanks

[whitebride91]

okay.. i found out that my car's temperature rises when i drive on small streets within 10 mins but on freeway it doesn't. it runs good on freeway. btw, im running without a thermostat cause it overheats within 3 mins at idle with it.

[PapaSmurf2k3]

Make sure you put the thermostat in with the dimple up top... it lets air escape. Did you bleed the system from the bleeder screw after filling it with coolant (its located kinda near the throttle body)? Have you verified that your fans are working correctly?

[whitebride91]

yep.. did everything. fans are fine too. just hope its not a cracked head or anything like that. its not smoking out from the muffler and theres no signs of oil in the radiator. HELP PLEASE!!!

[PapaSmurf2k3]

when it overheats, and you turn your heat on, does it blow hot air, or cold/normal temp?

[whitebride91]

it blows hot air

[PapaSmurf2k3]

ok, that means you shouldn't have any air bubbles in the system... the only other thing I can think of is if your radiator is damaged or something (not enough cooling capacity), or you have a flow restriction somewhere- Either internal (liquid), or external, airflow to your radiator.

Does the temp rise slowly, or does it shoot up quickly?

[whitebride91]

not too sure but i know its not slow. so its not the head gasket right? i hope not because i just bought the car for a couple of weeks.

[PapaSmurf2k3]

If you aren't burning any coolant, and you aren't mixing coolant and oil, probably not.

Is your "new" radiator plastic? Sometimes blown head gaskets can pressurize the coolant system which can blow a plastic radiator... but that usually happens mostly on Hondas. 240s just leak coolant.

[whitebride91]

yeah, its a plastic radiator. if my car still reads compression, then its not the head right? the compression test was about 170ish on all four.

[PapaSmurf2k3]

yeah that sounds pretty good. I'd be looking for a block/restriction myself.

[whitebride91]

still has the same problem. anything else i should/could do or check?

[PapaSmurf2k3]

I dunno, if your radiator is of questionable quality, you might want to upgrade to a bigass Koyo or something...

[navysnail]

what mix ratio of coolant to water are you using? and is your fan working?

[whitebride91]

the fan is fine and im runnin 50/50 on the coolant.

[whitebride91]

im about to do a coolant system pressure test this weekend.

[240user89]

you said you replaced your coolant temp sensor right?

[whitebride91]

havent changed it yet. should i? how much??

[PapaSmurf2k3]

Coolant temp sensors are probably about $35. It doesn't have anything to do with how hot your engine runs, it just adjusts your air/fuel ratios based on if your engine is warm or cold, or somewhere in between.

There is another sensor for the gauge though. Typically those are pretty reliable, and when they do go bad, they peg themselves out one way or the other (don't work at all, or are pegged completely over).

[whitebride91]

i havent done the pressure test yet but what does it mean when most of the radiator fluid goes to the reservoir. its almost to where it fulls the reservoir tank and when i pop the radiator cap after it cools down, it looks empty.

[dccse3k]

If its losing a lot of fluid it has to be a leak somewhere. Is there any dripping anywhere? If there isn't your head gasket might be cracked but you said you didnt see any steam coming out the exhaust right?

[whitebride91]

i dont see any leaks and i dont see any smokes from my exhaust or oil coolant mixture. it fills the reservoir tank almost to the top though, is it normal?

[PapaSmurf2k3]

yeah, mine fills it quite a bit.... does it drink it back once the car cools down?

[whitebride91]

well, i finally saw mines draining back the fluid but it still has the overheating problems. i think there might be a leak somewhere that i may not see. cant wait until my paycheck so i can look more into it.


Modified by whitebride91 at 7:23 PM 6/27/2009

[jemini91]

fluid is going to the resevoir because there is air in the system. when the car is cold you should take off the radiator cap and pour coolant until it is full and let it run until all the bubble come out. After you do this drive the car around with the heat on blast should fix the problem

[whitebride91]

i took my car to the shop and they did a leak down test on it. he said its 100% the head or the head gastket, one or the other and its leaking pressure into my cooling system. he recommended me to use BLUE DEVIL stop leak. this guy knows my dad for 20 years now and he's a good guy. what do you guys think?